In the field of computer-graphics, a character has been animated for various purposes. Whether or not the character be a human, an animal or an object, computer scientists and computer-graphics animators have attempted to animate the character as if it is capable of communicating with a viewer. At the infancy of computer graphics, the character generally teaches or entertains the viewer in a non-interactive manner without responding to the viewer. As computer graphics has matured, the character had been animated in a slightly interactive manner. To support such an interaction between the character and the viewer, the character image must be animated on a real-time basis.
Despite significant advances in hardware and software, real-time character animation is still a difficult task. Among various images to be animated, character, human or otherwise, generally requires complex calculations at a high speed for rendering a large number of image frames. In particular, to communicate with a viewer in an interactive manner, the character animation must be able to synchronize its lip movement with an audio output as well as to express complex motions. To accommodate such complex high-speed calculations, an expensive animation system including a high-performance processor is necessary. In addition, the complex input sub-system for inputting various information such as lip movements, limb movements and facial expressions are also necessary.
In the attempts to solve the above-described problems, the VACTOR.TM. system, includes a high-performance three-dimensional rendering unit along with a complex input sub-system. An character image is rendered on a real-time basis based upon the inputs generated by a special sensor gear that a performer wears. The special sensor gear includes a position sensor placed around the lips of the performer, and certain exaggerated mouth movements generate desired mouth position signals. The performer also wears another set of position sensors on limbs for signaling certain limb movements. However, it has been reported that these position sensor gears are not ergonomically designed and requires a substantial amount of training to generate desired signals. Furthermore, the cost of the VACTOR.TM. system is beyond the reach of most commercial enterprises and let alone individual consumers.
On the other hand, certain prior art two-dimensional animation systems do not generally require the above-described complex hardware and software and are usually affordable for the lack of realistic animation. For example, a two-dimensional character image is animated based upon the presence or the absence of a voice input. In this simplistic system, the mouth is animated open and closed during the voice input, and the animation is terminated when there is no more voice input. To animate the mouth, animation frames depicting the open mouth and the closed mouth is stored in an animation database, and upon the receipt of the voice input, an animation generator outputs the above-described animation frames to approximate the mouth movement in a crude manner. In other words, since this system has the same monotonous open and close mouth movement in response to various voice patterns, the animated character image fails to appear interactive. Furthermore, the image character generally fails to produce facial expressions.
As described above, the prior attempts have not yet solved the cost performance problem for a real-time animation system capable of generating a lively character image for communicating with a viewer using generally available personal computers such as IBM-compatible or MacIntosh. A method and a system of generating a real-time yet lively character image on a widely available platform would substantially improve a cost performance relation that the above-described prior attempts had failed.
The animation system satisfying the above-described cost performance relation has a wide variety of application fields. In addition to traditional instructional and entertainment applications, for example, such a character animation system may be used to promote products at trade shows, author a short animation for various uses such as games and broadcasting, as well as to interface an end user. The image character animation may be authored in advance of the use or may be generated in response to a viewer response in an interactive manner.